The present invention relates to cathode ray tubes for projection television systems. More particularly, the invention relates to means and method for conveniently and precisely aligning cathode ray tubes in projection television systems during manufacture and maintenance.
Precision aligning of projection tubes is essential in projection television systems. The television image that is electron-formed on the cathodoluminescent screen is projected a considerable distance onto a viewing screen and enlarged several times in the process. As a result, any appreciable error in alignment of a projection tube is similarly enlarged and amplified in the translation. Also, three discrete projection tubes are commonly used in a color system, and the images projected must appear in precise coincidence on the screen. Any appreciable error in the relative alignment of one or more of the tubes is amplified in projection, resulting in a degraded image on the screen.
Bennett et al in U.S. Pat. No. 3,369,881 discloses a method comprising the preparation of the funnel members and face panel members of cathode ray tubes for optimum alignment and sealing of such parts in the fabrication of tube envelopes. The method comprises the steps of forming complemental viewing panel portions and funnel portions by rectangular cathode ray tube envelopes. Each of the parts is formed with a plurality of external complemental reference protuberances. The reference protuberances on the funnel are used in the alignment of the neck and funnel prior to their conjoinment. Reference summits are ground on the protuberances on each funnel-neck part in accordance with a rotational and lateral alignment of the funnel, and in accordance with an axial alignment of the neck. Each pair consisting of a funnel and a face panel, may be optimally referenced to each other before sealing together by means of the reference summits, using a suitable fixture.
Fyler, in U.S. Pat. No. 2,961,560 discloses a color television picture tube which includes structural assemblies for retaining the aperture mask in a unique position relative to the phosphor dot screen. The major reference points for location of the mask are provided on or adjacent to the viewing end of the bulb. In one embodiment of the invention, cast projections are molded as part of the inner surface and are spaced about the periphery of the viewing end of the bulb. The aperture mask is provided with fittings which cooperate with the locating members. To maintain firm contact of the mask, fittings for the locating member springs are provided.
Faceplate-funnel referencing means are disclosed in U.S. Pat. No. 4,028,580 to Dougherty. A color cathode ray tube is depicted including a shadow mask and improved suspension devices for suspending the mask adjacent the faceplate of the tube. The disclosure stresses channel-shaped studs comprising parts of the suspension devices. Each of the studs has a first portion adapted to be imbedded in the faceplate and a second portion having provision for coupling the stud to the shadow mask. The studs engage reference surfaces on the inside of the funnel when the faceplate and funnel are mated and thereby serve to reference the faceplate to the funnel.